Breathing assistance apparatus

ABSTRACT

A nasal cannula for delivering respiratory gases to a neonatal infant comprising a manifold including a chamber, a gases inlet to the chamber and a gases outlet a low resistance path for gases through the chamber from its inlet to its outlet and a pair of nasal prongs in fluid communication with the chamber with each prong substantial equidistant the inlet, and directly in the low resistance path to deadspace eliminate.

FIELD OF INVENTION

[0001] This invention relates to Nasal Cannulae particularly though notsolely to nasal cannulae for delivering Continuous Positive AirwayPressure (CPAP) to neonates.

BACKGROUND

[0002] Certain individuals require a respiratory supplement such as air,oxygen, or other gases. Such gases are freely supplied and/or suppliedat controlled pressures. Such gases are also supplied through thepatient's mouth and/or through the patient's nose. Nasal supply systemsprovide an advantage in that they are generally more convenient and lessintrusive than mouth based or mouth covering devices. Despite theirconvenience, nasal based devices are deemed uncomfortable in light ofsecurement straps placed across the face and/or around the head and usedto secure the device to an individuals breathing cavity. Moreover,conventional cannulas do not provide a proper seal around the nares toinhibit apnoea and to provide a high flow system to stimulate thepatients breathing. Hence, even with such securement straps, these nasaldevices often dislodge from the breathing cavity. This is of particularconcern with children, infants, or the elderly who do not understand theimportance of keeping the nasal breathing device in place, whether it bea nasal CPAP or nasal cannula.

[0003] It is known to be beneficial and therapeutic to supply anindividual with a sufficient amount of respiratory airway pressure inorder to maintain a minimum level of air volume in the lungs. If the airvolume falls below this minimum level, then the lungs may collapse,which can be extremely dangerous or even deadly to the individual.Moreover, the back pressure can increase oxygen levels in the lungs anddecrease carbon dioxide levels. This will also improve PH by removal ofcarbon dioxide, which is an acid, from the blood. Hence, the applicationof such sufficient pressure, called continuous positive airway pressure(CPAP), has been found to be advantageous in maintaining a minimum airvolume or lung pressure when an individual is spontaneously breathing.CPAP can be supplied through nasal attachment devices such as a nasalcannulae, or through mouth based or endotracheal devices.

[0004] A number of CPAP devices are known including endotracheal tubes,head chambers, face chambers, face masks, nasal prongs, and nasalcannula. While each type of device has advantages and disadvantages, thenasal cannula provides a comfortable alternative for providing CPAPand/or airflow assistance. Prior art nasal cannulae have been disclosedin many forms with various methods of securing the device to the nasalpassageway. One such cannula assembly is disclosed in U.S. Pat. No.3,513,844 which uses an adjustable strap that encircles an individual'shead. A similar device is disclosed in U.S. Pat. No. 4,106,505 whereinthe supply tubes to the cannula are hooked over an individual's ears andaround the head. Even more cumbersome, U.S. Pat. No. 5,477,852 disclosesa device with a headband for holding and positioning the nasal insertsand associated supply tubes. Yet another system in U.S. Pat. No.5,271,391 discloses a cannula which is secured by applying strips ofpressure sensitive adhesive tape to the supply tubes leading from eachside of the cannula, thereby attaching the supply tubes to the cheeks ofan individual with the cannula positioned in between.

[0005] “Bonnet” type devices are also used to hold the CPAP nasalcannulae in place. However, this method generally puts pressure on anindividual's nose and upper lip thereby causing pressure necrosis in thecentre of the nose. A particularly sensitive individual is a youngchild, infant or baby. The bonnet also fails to adequately keep thenasal prongs in position, particularly with infants who move or rollaround in their crib. In a hospital or care facility setting, it is notuncommon for an attendant to discover that the CPAP device has beendisconnected from a patient's nose, which can lead to apnoea,desaturations, bradycardia, or hypoxia which is dangerously low oxygenlevels in the blood. In practice, the tubing for these bonnet typeCPAP's is draped around both sides of the patient's cheek which meansthat the most comfortable lying down position is on the patient's back.Pressure on the patient's cheeks caused by the securement device canmake other positions uncomfortable.

[0006] Other prior art anchoring systems include adhesive devices whichattach directly to the nose. U.S. Pat. No. 4,823,789 discloses a nosetube anchoring strip which has an adhesive coated sheet shaped to fitover an individual's nose and an appendage for holding a nasal-gastrictube. A similar system is found in U.S. Pat. No. 5,156,641 which has ananchoring cord adhesively attached to an individual's nose at one endand attached to hold a naso-gastric catheter at the other end. U.S. Pat.No. 5,513,635 provides a securement device with a body engagementportion which adheres across the nose of an individual with cannulaengaging portions extending down therefrom. Similarly, U.S. Pat. No.5,682,881 discloses the use of an adhesive foam pad secured to the upperlip for positioning of the cannula.

[0007] In U.S. Pat. No. 3,643,660 a unified nasal cannula comprises ahollow tubular body having an upper flat or plane surface and a pair ofspaced and curved elongated tubular extensions, having exterior orificesfor directing a gas flow which extensions project upwardly at an anglefrom the surface. Referring to FIGS. 2 and 3 we see that because theinlet 400 is from one side the prongs 402,404 may see slightly differentpressures. There is also the potential for downstream prong 404 torebreathe the expired CO₂ from upstream prong 402.

[0008] In U.S. Pat. No. 5,975,077 a cannula is disclosed including anairway injecting gas in fluid communication with nostrils of a patientand aerodynamically designed passageways for both the ambient air andthe injected gas to optimize the fluid flow characteristics duringinhalation and exhalation of the patient.

[0009] In U.S. Pat. No. 4,774,946 a cannula is described attached to anelongated flexible tube. The nasal prongs include bulbous portions thatseat and seal the nasal tubes in the nares.

[0010] In U.S. Pat. No. 5,193,532 a device is disclosed for generatingby ejector action a continuous positive airway pressure (CPAP),comprising a breathing-channel which at one end opens into theatmosphere and at another end is adapted to be provided with anattachment device to the nose and/or mouth of the patient as seen inFIG. 1. The inlet is situated between a channel open to the atmosphereand open to the prongs in such a manner that the stream of fresh gas isdirected mainly co-axially into the channel, producing an ejectoraction.

[0011] However, while these prior art systems do provide nasal CPAP theysuffer from a number of disadvantages including: insufficientlysecurement to the patients head, potential for unbalanced pressure ineach prong, and potential for rebreathing of expired CO₂.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a nasalcannula which goes someway to overcoming the above mentioneddisadvantages or which will at least give the public a useful choice.

[0013] Accordingly in a first aspect the present invention maybe broadlysaid to consist in nasal cannula for delivering respiratory gases to aneonatal infant comprising:

[0014] a manifold including a chamber, a gases inlet to said chamber anda gases outlet to said chamber, and a low resistance path for said gasesthrough said chamber from said inlet to said outlet

[0015] a pair of nasal prongs in fluid communication with said chambersubstantial equidistant said inlet, said prongs juxtaposed directly insaid path.

[0016] Preferably said cannula includes securement means to hold saidprongs in place in the nares of said neonate.

[0017] Preferably said securement means including a strap adapted topass around the back of the neck of said neonate and engage with saidcannula and thereby hold said prongs in place in the nares of saidneonate.

[0018] Preferably said strap includes a low resistance portion, said lowresistance portion adapted to engage with said cannula in a slidingfashion to allow said strap substantial lateral (iguanian axial)movement relative to said cannula.

[0019] Preferably said low resistance portion comprises a thin plasticstrand or strip.

[0020] Preferably the remainder of said strap includes an adjustableattachment to said low resistance portion to in use adjust the tensionof said strap.

[0021] Preferably said securement means including an infant bonnetcomprising head cover means adapted to at least partially cover the headof an infant and including at least a cuff of elastic property tosecurely locate said cover means on said infant head, and medical tubesecuring means connected with said cover means on the outer surfacethereof, said medical tubes adapted to in use connect to said cannula,said securing means operable to hold medical tubes passing over saidcover means against at least lateral (iguanian axial) movement.

[0022] Preferably said head cover means is formed of a knit fabric in atubular configuration and open at both ends, said securing means isconnected with said outer surface adjacent one said open end and endclosing means are connected with said outer surface adjacent the othersaid open end, said end closing means being operable to hold the saidknit fabric of its respective said end in a closed, bunched together,condition.

[0023] Preferably either or both of said tube securing means and saidend closing means arc or include a lace or tie stitched to said headcover means.

[0024] Preferably said lace or tieing is secured at its centre to saidhead cover means to provide two alms, said arms passing through atightening toggle slidable on said arms.

[0025] Preferably said tightening toggle is operable between at leasttwo conditions, being biased to a pinch off condition in which said armsof said lace or tie are clamped within their passage through said toggleand manipulable to a free configuration in which said toggle may slide along said arms of said lace or tie.

[0026] In a second aspect the present invention may be broadly said toconsist in a system for delivering respiratory gases in a neonatalinfant comprising

[0027] a source of pressurised gases,

[0028] an inhalatory conduit in fluid communication with said source ofgases and adapted to convey gases,

[0029] a nasal cannula in fluid communication with said inhalatoryconduit and adapted to deliver gases to the nasal passages of saidinfant,

[0030] an exhalatory conduit in fluid communication with said deliverymeans and adapted to convey gases from said delivery means, and

[0031] a pressure regulating device disposed within or in fluidcommunication with said exhalatory gases transport means and adapted toachieve a predetermined mean pressure of gases delivered to the nasalpassages of said infant by regulating the flow of gases through saidpressure regulating device.

[0032] Preferably pressure regulating device comprising:

[0033] a container adapted to house a body of liquid,

[0034] terminal conduit means including proximate and distal ends, saidproximate end adapted for connection to said exhalatory conduit, andsaid distal end adapted for submergence in said body of liquid,

[0035] such that in use the mean pressure of gases delivered to thenasal passages of said infant is determined by the level to which saiddistal end is submerged in said body of liquid.

[0036] To those skilled in the art to which the invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the scope of the invention as defined in the appended claims. Thedisclosures and the descriptions herein are purely illustrative and arenot intended to be in any sense limiting.

[0037] The invention consists in the forgoing and also envisagesconstructions of which the following gives examples.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] One preferred form of the present invention will now be describedwith reference to the accompanying drawings in which:

[0039]FIG. 1 is a side view of a prior art cannula on an infant,

[0040]FIG. 2 is a perspective view of a prior art cannula on an infant,

[0041]FIG. 3 is a cross section of a prior art cannula,

[0042]FIG. 4 is a closeup perspective view from above of the presentinvention,

[0043]FIG. 5 is a section view of the present invention,

[0044]FIG. 6 is a closeup perspective view of the present invention,

[0045]FIG. 7 is a side view of the present invention,

[0046]FIG. 8 is a closeup view of the present invention from below,

[0047]FIG. 9 is a closeup view of the present invention from above,

[0048]FIG. 10 is an illustration of the present invention is use on anneonate,

[0049]FIG. 11 is a block diagram of the CPAP system,

[0050]FIG. 12 is a side view of the bonnet, and

[0051]FIG. 13 is an illustration of the bonnet is use on an neonate

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] Referring now to FIG. 11 in which a typical application isdepicted. A humidified Continuous Positive Airway Pressure (CPAP) systemis shown in which a patient 19 is receiving humidified and pressurisedgases through a nasal cannula 28 connected to a inhalatory conduit 21.It should be understood that the present invention, however, is notlimited to the delivery of CPAP gases but is also applicable to othertypes of gases delivery systems. Inhalatory conduit 21 is connected tothe outlet 12 of a humidification chamber 10 which contains a volume ofwater 15. Inspiratory conduit 21 may contain heating means or heaterwires 20 which heat the walls of the conduit to ensure a constanthumidity profile along the conduit and therefore reduce condensation ofhumidified gases within the conduit. As the volume of water 15 withinhumidification chamber 10 is heated, water vapour begins to fill thevolume of the chamber above the water's surface and is passed out of thehumidification chamber 10 outlet 12 with the flow of gases (for exampleair) provided from a gases supply means or blower 18 which enters thechamber 10 through inlet 16.

[0053] The humidified gases pass through the inhalatory conduit 21 tothe cannula 100 connected to the patient's 19 nose through prongs116,118. The expired gases pass through the prongs 116,118 to the outputmanifold 130. The excess gases then flow through the exhalatory conduit230 to a pressure regulator 234.

[0054] In the preferred embodiment of the present invention the pressureregulator 234, takes the form of discharging the flow of exhalatorygases into a chamber 204 containing a column of water 238 as seen inFIG. 11. The gases flowing through the exhalatory conduit 230 aredischarged into the body of water 238 from a short conduit 236 whichextends from the expiratory conduit into the chamber 204. This resultsin a bubbling effect, whereby the gases eventually exit the chamber 204via the outlet port 252, which can also be used to initially fill thechamber 204 with water. The outlet port 252 includes shielding toprevents liquid aerosols created by the vigorous bubbling on the surfaceof the water from being expelled. It will be appreciated that the shortconduit 236, could equally be integrated into the end of the expiratoryconduit 230. It will also be appreciated that by adjusting the level ofwhich the short conduit 236 is submerged in the body of water 238 themean pressure of supplied gases through the cannula 100 can becontrolled.

[0055] Nasal Cannula

[0056] Referring now to FIGS. 4 to 10 the nasal cannula 100 is seen inmore detail. The inlet manifold 110, includes an inlet port 112. Thisaccepts the gas flow from the humidifier and air/oxygen blender or anyother flow source apparatus as would be appropriate. The diameter of theinlet manifold 110 is as large as possible to ensure minimal pressuredrop in the gases before delivery to the patient. In fluid communicationwith the inlet manifold are two nasal prongs 116, 118. The gases arethen able to flow from the inlet manifold 110 up through the nasalprongs into the corresponding nares of the patient. The prongs 116, 118themselves are cylindrical with a slight taper narrowing at the top. Thediameter is carefully chosen such that it will substantially sealagainst the interior of the nare, without imparting any substantialpressure thereon. As well as sealing this also provides some level ofsecurement and keeps the cannula 100 in place.

[0057] An important feature of the present invention is shown in FIG. 2and in more detail in FIG. 3. The two nasal prongs 116, 118 are spacedapart at a distance optimised for the nare spacing for a neonatalinfant. However the present invention would be equally applicable forpatients of all sizes and the design is easily scalable. It will beappreciated that while the nasal structure of each infant will besomewhat different, almost inevitably the septum will be lower than hefleshy parts on the side of the nose. As mentioned in the discussion ofthe prior art this may result in irritation and pressure necrosis on theseptum. It can be seen that the inlet manifold 110 has a notch 126 orindentation in its uppermost portion between the two nasal prongs 116,118. The indentation 126 is designed such that there will be no contactwith the septum.

[0058] Referring now particularly to FIG. 5 showing a sectional view ofthe cannula 100. The inlet manifold 110 is separated from the outletmanifold 130 by a partition 132 running horizontally the length of bothmanifolds. The partition 132 terminates approximate to the base 134 ofthe prongs 116, 118. In this fashion there will always be at least someflow flowing directly from the inlet manifold 110 to the outlet manifold130. This ensures that the deadspace or tidal volume is limited to thevolume of the prongs 116,118. This configuration results in the minimumbuild up of expired CO₂ and also reduces any opportunity forcondensation in the cannula 100.

[0059] The prongs 116, 118 are made from a moulded rubber or siliconinsert 136 which has an interference or compression fit seal to the hardplastic body 138 of the cannula 100. The prongs are able to be used as adisposable component or alternatively easily interchangeable fordifferent sizes, a nasal mask, mouthpiece or other interface as desired.The inlet port 112 connects directly to inlet manifold 110 and may beprovided with any typical connection configuration for commerciallyavailable conduits. Similarly the outlet port 142 is in fluidcommunication with the outlet manifold 130. A further sensor port 144 isprovided to measure any parameters of the delivered gases for examplepressure, temperature, humidity. An integral 10mm inlet 10 mm outletconduit 154 formed from extruded PVC or silicon was found to be suitablefor this purpose. The sensor port 144 is connected to a measurement tube156 which may also form part of the integral inlet outlet tube 154connected to the cannula 100.

[0060] Head Securement

[0061] As can be seen in FIGS. 10 to 12 the cannula 100 is secured tothe neonates head by a bonnet overs its head. The infant bonnet of thepresent invention includes a head covering portion 330 which ispreferably formed of a stretchable or elastic material having thermalinsulation property. An example of appropriate material is a syntheticor cotton knit fabric. The head covering 330 is provided in the form ofa open ended tube. Where the material of the covering 330 provides morestretch along one principal axis then that principal axis as preferablyaligned across the axis of the tube.

[0062] The head covering 330 preferably includes a zone adjacent oneopen end 332 which is stiffer than the surrounding region. The zone 331may comprise for example a region of modified knit form a cuff formedfrom an alternate material or material configuration or a multi layerhem of the tube.

[0063] A securing device is provided on the outer surface of thecovering 330 for supporting a breathing tube or other medical conduitsor wiring.

[0064] The securing means is a strap 333 with which is sewn onto thebonnet. The strap has Velcro attached at one end. The nasal tubing isfitted with a foam block 334 with a triangular outside shape. The foamblock 334 is positioned on the strap 333. The strap 333 is then closedaround the foam block and secured with the Velcro. The foam block 334 isused to firmly hold the nasal tubing 321 in place on the bonnet 330 toprevent displacement of the nasal prongs from the nares.

[0065] The second open end 347 of the head coveting 330 is preferablyformed with a simple hem. The open end 347 is preferably closeable orretainable in a closed position by a closing means 340. The closingmeans 340 may comprise a further lace or tie of similar configuration tothe securing means 333. The lace or tie 340 has two arms 342, 344. Thearms 342, 344 preferably tie together or pass through a toggle.

[0066] In use the end 347 of head covering 330 is bunched together as anend bunch 341. The loop of lace or tie 340 is passed over the bunch 341.The bunch 341 is firmly secured in a closed configuration within thetightened loop of the lace or tie 340.

[0067] The closing means 340 thus provides for easy and efficientclosing or opening of the infant bonnet should there be a need foraccess to the top of the head of the infant. Access may for example berequired for placement of electrodes or for cranial ultrasounds. Whereaccess is required the closing means 340 may be released and the bunchedportion of end 347 opened to provide necessary access. This access isavailable without disturbing the other end 332 of the head covering 330or the securing means 333 supporting medical tubes or wires in place.

[0068] Cannula Securement

[0069] Ideally the neonate should not be breathing out of its mouth.Both inhalation and exhalation should be done through the cannula. Inthe preferred embodiment the neonates jaw is strapped shut to eliminatemouth leak. Mouth leak is undesirable because it causes a lower pressurethus reducing the level of CPAP.

[0070] Referring now particularly to FIGS. 8 to 10 we see that thecannula 100 is secured at its base to the back of the neonates headusing strap 150. The strap connects at the base of the neonates skull onthe back of the neck. It connects to the cannula 100 by way of a slidingstrap 152. This strap is secured by way of clips to the hard plasticbody 138 allowing the securing strap 150 substantial relative movementwith respect to the cannula 100 as the neonate twists its head whileproviding adequate restraining force directly on the cannula 100 withoutany twisting of the cannula 100. In one embodiment this is accomplishedby a plastic e.g. acetal sliding strap which engages into sliding clipson the outer face of the cannula. The teflon strap is adjustablyattached to the neck strap 150 to allow the tension to be adjusted to acomfortable level.

[0071] What has been described is an improved nasal cannula for use witha CPAP respirator. The improvement reduces the likelihood of pressurenecrosis or irritation that might normally be associated with the use ofsuch a device. The improvement ensures a balanced feed to both prongs,low deadspace high flow through the manifold so rebreathing of expiredCO₂ is minimised.

1. A nasal cannula for delivering respiratory gases to a neonatal infantcomprising: a manifold including a chamber, a gases inlet, a gasesoutlet and a low resistance path for said gases through said chamberfrom said inlet to said outlet a pair of nasal prongs in fluidcommunication with said chamber substantial equidistant said inlet, saidprongs juxtaposed directly in said path.
 2. A nasal cannula fordelivering respiratory gases to a neonatal infant as claimed in claim 1wherein said cannula includes securement means to hold said prongs inplace in the nares of said neonate.
 3. A nasal cannula for deliveringrespiratory gases to a neonatal infant as claimed in claim 2 whereinsaid securement means including a strap adapted to pass around the backof the neck of said neonate and engage with said cannula and therebyhold said prongs in place in the nares of said neonate.
 4. A nasalcannula for delivering respiratory gases to a neonatal infant as claimedin claim 3 wherein said strap includes a low resistance portion, saidlow resistance portion adapted to engage with said cannula in a slidingfashion to allow said strap substantial lateral (egonon axial) movementrelative to said cannula.
 5. A nasal cannula for delivering respiratorygases to a neonatal infant as claimed in claim 4 wherein said lowresistance portion comprises a thin plastic strand or strip.
 6. A nasalcannula for delivering respiratory gases to a neonatal infant as claimedin claim 5 wherein the remainder of said strap includes an adjustableattachment to said low resistance portion to in use adjust the tensionof said strap.
 7. A nasal cannula for delivering respiratory gases to aneonatal infant as claimed in anyone of claims 2 to 6 wherein saidsecurement means including an infant bonnet comprising head cover meansadapted to at least partially cover the head of an infant and includingat least a cuff of elastic property to securely locate said cover meanson said infant head, and medical tube securing means connected with saidcover means on the outer surface thereof, said medical tubes adapted toin use connect to said cannula, said securing means operable to holdmedical tubes passing over said cover means against at least lateral(egonon axial) movement.
 8. A nasal cannula for delivering respiratorygases to a neonatal infant as claimed in claim 7 wherein said head covermeans is formed of a knit fabric in a tubular configuration and open atboth ends, said securing means is connected with said outer surfaceadjacent one said open end and end closing means are connected with saidouter surface adjacent the other said open end, said end closing meansbeing operable to hold the said knit fabric of its respective said endin a closed, bunched together, condition.
 9. A nasal cannula fordelivering respiratory gases to a neonatal infant as claimed in claim 8wherein either or both of said tube securing means and said end closingmeans are or include a lace or tie stitched to said head cover means.10. A nasal cannula for delivering respiratory gases to a neonatalinfant as claimed in claim 9 wherein said lace or tieing is secured atits centre to said head cover means to provide two arms, said armspassing through a tightening toggle slidable on said arms.
 11. A nasalcannula for delivering respiratory gases to a neonatal infant as claimedin claim 10 wherein said tightening toggle is operable between at leasttwo conditions, being biased to a pinch off condition in which said armsof said lace or tie are clamped within their passage through said toggleand manipulable to a free configuration in which said toggle may slide along said arms of said lace or tie.
 12. A system for deliveringrespiratory gases in a neonatal infant comprising a source ofpressurised gases, an inhalatory conduit in fluid communication withsaid source of gases and adapted to convey gases, a nasal cannula influid communication with said inhalatory conduit and adapted to delivergases to the nasal passages of said infant, an exhalatory conduit influid communication with said delivery means and adapted to convey gasesfrom said delivery means, and a pressure regulating device disposedwithin or in fluid communication with said exhalatory gases transportmeans and adapted to achieve a predetermined mean pressure of gasesdelivered to the nasal passages of said infant by regulating the flow ofgases through said pressure regulating device.
 13. A system as claimedin claim 12 wherein pressure regulating device comprising: a containeradapted to house a body of liquid, terminal conduit means includingproximate and distal ends, said proximate end adapted for connection tosaid exhalatory conduit, and said distal end adapted for submergence insaid body of liquid, such that in use the mean pressure of gasesdelivered to the nasal passages of said infant is determined by thelevel to which said distal end is submerged in said body of liquid. 14.A system in as claimed in claim 13 wherein said nasal cannula isconstructed according to any one of claims 1 to 11.